This application corresponds to and claims priority to Italian Application No. T099A001040, filed Nov. 26, 1999. This Italian application is hereby incorporated by reference as though fully set forth herein.
The present invention relates to devices for metering flowable products, the term xe2x80x9cflowable productsxe2x80x9d here being used to indicate products such as products in the form of powder, granules, or microspheres that are to be conveyed by getting them to flow. Products of this sort are widely used, for instance, in the chemical industry, the foodstuffs industry, or (with reference to the sector of application which will be referred to more than once in what follows, without, at the same time, this implying any limitation of the scope of the invention) in the textile industry, in particular in plants for the preparation of treatment baths, such as baths for dyeing.
A solution widely adopted in the known art envisages that the products in question be stored in containers that basically resemble tanks, equipped, in their bottom part, with a metering outlet. Associated to the latter there is usually a motor-driven member, such as a screw conveyor, the operation of which produces the controlled output of the material that is in the container.
In the recourse to this type of solution various problems are encountered.
In the first place, it is essential to ensure the precision of the metering action. The exact quantity of material delivered represents in fact a determining factor for the end result that is sought. A high metering precision may be achieved using dispensing members of small dimensions. This choice, however, runs up against the need to ensure adequate metering rates, which are of importance, for example, when metering the main components of a mixture.
In the second place, the majority of flowable products referred to previously (usually fine powders or hygroscopic materials, or again materials treated in such a way as to reduce their tendency towards dispersion in the environment in a volatile form) tend to agglomerate or, as is often said, xe2x80x9cpack togetherxe2x80x9d in the storage container. For this reason, the containers referred to are usually equipped, above the metering outlet, with agitating members, such as mechanical agitators, basically resembling crank shafts.
In EP-A-0 943 368 (used as reference for the preamble of Claim 1) there has already been proposed a device comprising at least one chamber that defines a respective passage for the materials being metered and is limited by at least one wall that can be moved according to a vibratory motion, usually exerted by a device for generating vibrations of a mechanical type.
The results that may be achieved with this known solution are to be deemed certainly satisfactory, also as regards the possibility of obtaining a fine proportioning of the product being delivered. There exists, however, the need to improve the operating characteristics of the said device further, above all as regards operation in the presence of high rates of delivery, without this proving prejudicial to the possibility of performing a fine metering action.
The purpose of the present invention is to provide a metering device of the type specified above, further improved from this and other points of view.
According to the present invention, this purpose is achieved thanks to a device having the characteristics referred to in the ensuing claims.